Modern cancer research requires state-of-the-art cell and tissue imaging technology. These techniques include immuno-localization studies at both the light and electron microscopic levels, live cell studies using molecules tagged with fluorescent probes (fluorescein, GFP, etc.) and introduced by transfection or microinjection, and advanced image recording and analysis. Sophisticated imaging instruments such as electron microscopes, confocal and multi-photon microscopes are not only very expensive, but also require technical assistance for optimal results. For these reasons, it is essential to have a core imaging facility that provides access to both the instruments and technical expertise. Established 20 years ago as a departmental service, the Cell Imaging Facility has evolved into a Medical School Core Facility that enjoys support from the medical school, the Vice President for Research at NU, and the Robert H. Lurie Comprehensive Cancer Center. The Facility?s full time Director, Dr. Weiming Yu, Ph.D.,is an expert in all aspects of light microscopic imaging, especially fluorescence and multi-photon microscopy. A full time electron microscope technologist is also available to perform routine cell and tissue embedding and sectioning as well as advanced techniques such as immuno-gold localization, and to train users in these techniques. The facility serves several hundred users from about 75 research groups throughout the University. Over the past three years over 52 percent of total facility usage has been by Cancer Center members with peer reviewed funding. Equipment includes two transmission electron microscopes, two confocal microscopes, three advanced light microscopes with digital imaging systems and capabilities that include microinjection, epifluorescence, time lapse photography, calcium imaging, FRAP, and FRET. Ancillary equipment includes rotary shadowing evaporators, microtomes, color printers, digital scanner, film recorder, dark room, and computers and software for image analysis. Plans are in place to build a-state-of-the art multi-photon light microscope and to increase imaging modalities by working closely with individual investigators.